<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    p {
      width: 200px;
      height: 200px;
      background-color: red;
    }
  </style>
</head>
<body>
  <!-- 1、p标签中不要再嵌套div、p、h等块级元素 -->
  <!-- <p>
    <div></div>
  </p> -->

  <!-- 2、a标签不能嵌套a标签 -->
  <a href="#">
    <a href="#">我是一个a标签</a>
  </a>

</body>
</html>